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When it comes to installing a new flooring material, you sometimes have the option of installing the underlayment for your new floor directly on top of the existing installation. However, in most cases it requires complete removal of the existing flooring before you can install the underlayment for your new installation, and it is important to know in which cases you need to do which to preserve the integrity of the new installation.

Materials Requiring Underlayment

The first step in determining if you can lay underlayment for your new installation down on top of an existing flooring installation is looking at the type of flooring material you are installing. Laminate flooring, for example, is usually installed in a floating format, and any underlayment is usually foam padding that simply protects against noise. Hardibacker or concrete boards for ceramic tile, on the other hand, provide a stable base for the tile installation, which means the existing flooring needs to be taken into consideration.

Movement Equals Cracking

For some installations, such as ceramic and porcelain tiles or natural stones like slate and granite, movement equals the destruction of the installation. Since these are concrete-based installations, they are meant to be installed on a completely solid underlayment surface. In most cases, you cannot install underlayment for tile on top of an existing floor because the risk of movement between the subfloor, existing installation, underlayment and finish installation is too great, and the resulting project would simply crack out in a few weeks or months.

Basic Rule of Thumb

The basic rule of thumb when checking to see if you can lay underlayment down on top of an installation is to check to see if your new finish product is reliant on movement for its structural integrity. Carpet installations, for example, do not care if the floor moves, so a carpet padding underlay will not be affected by the existing installation. Floating wood floor installations are similar in that they simply rest on top of the existing install, not rely on it for strength and stability. If movement is bad for the installation, chances are you cannot install an underlayment and new product directly on top of an existing one.

Manufacturer Warranty

When in doubt, check the manufacturer guidelines for your new product. They will clearly state the underlayment requirements for that particular product. It is vitally important that you follow manufacturer guidelines to the letter when installing a new product or you will completely void any warranties associated with that product. If your manufacturer says you can put underlayment down on top of an existing install, you are good to go, but if not, you will need to completely remove the existing flooring back down to the subfloor for a proper, warrantied installation.

About the Author

Tim Anderson has been freelance writing since 2007. His has been published online through GTV Magazine, Home Anatomy, TravBuddy, MMO Hub, Killer Guides and the Delegate2 group. He spent more than 15 years as a third-generation tile and stone contractor before transitioning into freelance writing.